I got it quite by accident, really. My mom would let me order from the scholastic book club, but she always had to have me shave a few off the list. Out of all the books I ordered over those years, that one sticks with me the most as an adult, and I think it would appeal to an adult on first reading, too.
Of course, I have fond memories also of Mystery of the Witches Bridge, The Wednesday Witch, and Hex House, and The Secret Tree House. Do I see a theme?